The census for the first time counted migrant workers where they lived and worked rather than where they are officially registered.
It found that more than 220 million Chinese had worked away from home for six months or more in 2010, almost double the previous figure.
High levels of urbanisation are the result of greater job opportunities and better educational and health services in the cities.
The proportion of people aged 14 or younger was 16.6 per cent, down by 6.29 percentage points from the last census in 2000.
The number aged 60 or older grew to 13.26 per cent, up almost 3 percentage points.
The rapid rise in average age is raising concerns about China’s capacity to sustain the high levels of growth it has had in the past 30 years, based largely on migrant labour employed in factories and construction since dwindling number of young workers will have to support a growing number of the elderly.
For many, this is the result of the government’s one-child policy. The average household now numbers 3.1 people, down from 3.44 a decade ago.
Increasingly, Chinese media are calling for a halt to the one-child policy, which was introduced in the 1980s to manage population growth at a time of slow economic development and widespread poverty.
Speaking at a recent meeting of Communist Party leaders, President Hu Jintao backed continuation of the current policy to keep population growth low.
Some experts say that it is “significant” that the issue has even been raised, given the fact that hitherto the government’s population policy was taken for granted.
According to government estimates, at least 400 million births were prevented under the one-child policy and that this played a key role in stimulating economic growth and reducing poverty.
Other analysts believe that the same policy has undermined China’s traditional extended family, giving rise a generation of single children who will have to care for their parents.
Hu himself acknowledged the problem when he said that social security and elderly care have to be improved, Xinhua reported on Tuesday.
The one-child policy has led to selective female feticide as well. Currently, six boys are born for every five girls.The same policy has often been enforced with violence, with some women subjected to forced abortion.